1. Field of the Invention
The present application relates to catheters, cannulae, endoscopes, and fiberoptic delivery systems of various forms of light, including laser, and particularly to a guidance system for directing such devices through the vascular system from a position external to the body.
2. Description of the Background Art
Many commerically available catheters and endoscopes exist for introducing into the vasuclar system a variety of surgical tools and materials, such as radiographic contrast materials, angioplasty baloons, fiberoptic cameras and lights, laser light, and a wide array of cutting instruments. These catheters and endoscopes are constructed to have good torque and rotational control in addition to advance and withdraw capabilities.
However, these catheters and endoscopes lack the ability to negotiate a tortuous course, i.e., trackability or steerability. Such catheters and endoscopes lack the ability to control vertical and horizontal movement of the tip of the device. For convenience of description, the term catheter will be used hereinafter. To overcome this problem, a series of catheters having different tip shapes, sizes, and stiffness are introduced on a flexible guide wire in order to appropriately deflect the tip in the proper direction.
Other attempts have been made in the past to provide catheters having distal ends which, when inserted into a body, are manipulatable to advance the catheter through body cavities. Catheters have been developed to include permanent magnets and employ magnetic fields to bend the distal end of the catheter. However, these devices are quite difficult to control and manipulate. Other catheters include fluid conduits to expand the distal end, but not to guide the distal end of the catheter.
Some work has been done to produce catheters which are readily insertable while being effectively anchorable in a body cavity. For example, the distal end of a catheter may be formed into a desired shape by using a material exhibiting mechanical memory that is triggered by heat. By heating the mechanical memory material, the distal end of the catheter is shaped to anchor the catheter within the body. However, the change of the shape or other movement of the distal end in these prior devices is limited to a single direction. Once the memory material has been heated causing the distal end to move in said single direction to assume its characteristic anchoring shape, it becomes necessary to deform the distal end manually at a temperature below the transition temperature of the mechanical memory material in order to change the shape of the distal end. The need for manual manipulation of a catheter once it is inserted into a body limits the steerability and aimability of the catheter.
U.S. Pat. Nos. 4,543,090, 4,601,705, and 4,758,222, all to McCoy, teach a catheter including an elongated tubular member having a proximal end and a distal end for insertion into the body and a plurality of temperature-activated memory elements in the distal end of the tubular member. Each memory element assumes a first shape when heated to a predetermined temperature. Each memory element is coupled to at least one other memory element so that movement of one element results in movement of the other element. Each memory element is moved to a second shape when the memory element coupled thereto is heated to the predetermined temperature. A control system adjacent the proximal end of the tubular member allows an operator to selectively control the temperature of each temperature-activated element to deflect the distal end of the tubular member so as to direct the course of the tubular member toward an organ or tissue within the body. The control system includes a power supply source, electrical connections between the power supply source and the memory elements in the distal end of the tubular member, and a control device for selectively applying power to heat the memory elements to their predetermined temperatures to deflect the distal end of the tubular member so as to steer the tubular member or aim the distal end of the tubular member within the body.
U.S. Pat. No. 4,636,195 to Wolinsky teaches a catheter having distal and proximate balloon segments expansible to produce a chamber around arterial plaque and a conduit for delivering solubilizing liquid into the chamber. The catheter may also contain a central expansible balloon to assist in forcing the liquid into the plaque and to compress the plaque. Several solubilizing liquids are described.
Technology exists for manufacturing small catheters having multiple lumens or channels. In addition, technology exists for the delivery of fluids to small inflatable balloons located at the end of a catheter to achieve angioplasty.
Manufacturers of gastrointestinal fiberoptic endoscopes have developed extremely sophisticated mechanical means involving cables and wheels to achieve tip mobility in their endoscopes. To date, no one has been able to transfer this technology to a vascular catheter because of the catheter's inherently small size, the extreme flexibility required to negotiate the vascular system, and the extreme length required to reach the coronary arteries from peripheral location such as the femoral artery in the groin.
Thus, there is a need for an aimable and steerable guidance system for a vascular catheter that may be less than 1 mm in diameter, extremely flexible, and very long.